PROJECT SUMMARY Links between affect, executive function, and prefrontal structure in aging have been suggested in many studies that capitalize on between-individual differences within cross-sectional designs. The proposed study investigates whether these associations can be replicated using a longitudinal design that can capitalize on within-individual change as well as between-individual differences. Using existing MRI and behavioral data that were collected for other purposes, the proposed research will assess whether affective change relates to executive change in older adults (Aim 1) and whether these changes are mediated by changes in cingulate or prefrontal structure (Aim 2). There has not yet been a longitudinal analysis of how changes in brain structure relate to affective as well as cognitive change in older adults, and thus there is much to be learned from this approach. If the results confirm the associations revealed in cross-sectional studies, this would provide a strong foundation for future research to examine questions such as: whether a change in these associations could be a biomarker for pathological aging; whether lifestyle or other interventions that preserve or enrich older adults? executive function also have positive impacts on their affective wellbeing; or whether there are age-related trajectories that set individuals at risk for affective disorders. If the results do not confirm the associations revealed in cross-sectional data, this would lead to an equally important future direction for research: to examine whether there are particular age bands over which the associations hold, or subsets of participants for whom the associations are strong, or whether theories of these associations need to be modified to explain associations that are driven by variability between, but not within, individual.